ZCZC MIATCDAT2 ALL TTAA00 KNHC DDHHMM TROPICAL STORM KARL DISCUSSION NUMBER 23 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122016 1100 PM AST MON SEP 19 2016 Karl is a little better organized tonight. An area of deep convection has been persisting during the past several hours, and microwave images indicate that the center is located near the southwestern edge of the convective area. The initial wind speed is nudged upward to 40 kt, following a blend of the latest Dvorak classifications from TAFB and SAB. Karl is moving west-northwestward at 11 kt, and it is being steered by the flow on the south side of a high pressure system over the subtropical Atlantic. The tropical cyclone is expected to move near the southwestern periphery of the high in a couple of days and then head toward a pronounced weakness in the ridge over the western Atlantic. This change in the steering pattern should result in Karl turning northwestward in about 48 hours, with a gradual turn to the north and northeast expected in 4 to 5 days. Although the models agree on the overall theme, there is a fair amount of spread in the guidance associated with where and when Karl begins to recurve. The NHC official track forecast is near the middle of the guidance envelope, and is in best agreement with the various consensus aids. The vertical wind shear that has been affecting Karl for the past several days appears to be letting up some, and the SHIPS model suggests that shear should be generally light during the next 5 days. In addition, Karl is currently over SSTs of around 28 deg C, and it is expected to move over even warmer waters throughout the forecast period. The one unfavorable parameter for intensification is the dry mid-level environment surrounding the tropical storm, but some of the guidance suggests that the air mass could moisten ahead of the system later this week. Based on these large scale conditions, slow strengthening seems likely during the next day or so, followed by a faster rate of intensification thereafter. The NHC intensity forecast is higher than the previous one, but is on the conservative side of the guidance at the longer range forecast points. FORECAST POSITIONS AND MAX WINDS INIT 20/0300Z 19.7N 50.5W 40 KT 45 MPH 12H 20/1200Z 20.4N 52.4W 45 KT 50 MPH 24H 21/0000Z 21.3N 54.9W 45 KT 50 MPH 36H 21/1200Z 22.4N 57.3W 50 KT 60 MPH 48H 22/0000Z 23.9N 59.7W 55 KT 65 MPH 72H 23/0000Z 26.7N 63.5W 70 KT 80 MPH 96H 24/0000Z 29.5N 64.5W 85 KT 100 MPH 120H 25/0000Z 32.3N 60.3W 95 KT 110 MPH $$ Forecaster Cangialosi NNNN
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